[DL]: Handle commit() calls that happen on the same frame as activation

It's possible to be in a committing state without having a commit
promise resolver, if the commit is caused by activation. This causes
problems with commit() calls that happen on the same frame as
activation-induced commit, as it expects the resolver to exist.

This CL handles that case and adds a test.

Bug: 953614
Change-Id: I83ba0b6e450672588ff960389fc045be4896fe32
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1573425
Reviewed-by: Chris Harrelson <chrishtr@chromium.org>
Reviewed-by: Fergal Daly <fergal@chromium.org>
Commit-Queue: Rakina Zata Amni <rakina@chromium.org>
Cr-Commit-Position: refs/heads/master@{#652473}
4 files changed